--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2010-12-19  Bruno Haible  <bruno@clisp.org>
+
+	fchdir: Add missing declaration on OSF/1 5.1.
+	* lib/unistd.in.h (fchdir): Provide declaration if systems lacks it.
+	* m4/fchdir.m4 (gl_FUNC_FCHDIR): Check whether fchdir is declared.
+	* m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Initialize HAVE_DECL_FCHDIR.
+	* modules/unistd (Makefile.am): Substitute HAVE_DECL_FCHDIR.
+	* doc/posix-functions/fchdir.texi: Mention the OSF/1 5.1 problem.
+
 2010-12-19  Bruno Haible  <bruno@clisp.org>
 
 	relocatable-prog-wrapper: Separate from relocatable-prog.

--- a/doc/posix-functions/fchdir.texi
+++ b/doc/posix-functions/fchdir.texi
@@ -12,6 +12,9 @@
 This function is missing on some platforms:
 Tandem/NSK, mingw, BeOS.
 But the replacement function is not safe to be used in libraries and is not multithread-safe.
+@item
+This function is not declared on some platforms:
+OSF/1 5.1.
 @end itemize
 
 Portability problems not fixed by Gnulib:

--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -435,6 +435,10 @@
 _GL_EXTERN_C int _gl_register_dup (int oldfd, int newfd);
 _GL_EXTERN_C const char *_gl_directory_name (int fd);
 
+# else
+#  if !@HAVE_DECL_FCHDIR@
+_GL_FUNCDECL_SYS (fchdir, int, (int /*fd*/));
+#  endif
 # endif
 _GL_CXXALIAS_SYS (fchdir, int, (int /*fd*/));
 _GL_CXXALIASWARN (fchdir);

--- a/m4/fchdir.m4
+++ b/m4/fchdir.m4
@@ -1,4 +1,4 @@
-# fchdir.m4 serial 14
+# fchdir.m4 serial 15
 dnl Copyright (C) 2006-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,6 +9,12 @@
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
   AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
+
+  AC_CHECK_DECLS_ONCE([fchdir])
+  if test $ac_cv_have_decl_fchdir = no; then
+    HAVE_DECL_FCHDIR=0
+  fi
+
   AC_CHECK_FUNCS_ONCE([fchdir])
   if test $ac_cv_func_fchdir = no; then
     HAVE_FCHDIR=0

--- a/m4/unistd_h.m4
+++ b/m4/unistd_h.m4
@@ -1,4 +1,4 @@
-# unistd_h.m4 serial 49
+# unistd_h.m4 serial 50
 dnl Copyright (C) 2006-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -126,6 +126,7 @@
   HAVE_UNLINKAT=1;        AC_SUBST([HAVE_UNLINKAT])
   HAVE_USLEEP=1;          AC_SUBST([HAVE_USLEEP])
   HAVE_DECL_ENVIRON=1;    AC_SUBST([HAVE_DECL_ENVIRON])
+  HAVE_DECL_FCHDIR=1;     AC_SUBST([HAVE_DECL_FCHDIR])
   HAVE_DECL_GETDOMAINNAME=1; AC_SUBST([HAVE_DECL_GETDOMAINNAME])
   HAVE_DECL_GETLOGIN_R=1; AC_SUBST([HAVE_DECL_GETLOGIN_R])
   HAVE_DECL_GETPAGESIZE=1; AC_SUBST([HAVE_DECL_GETPAGESIZE])

--- a/modules/unistd
+++ b/modules/unistd
@@ -100,6 +100,7 @@
 	      -e 's|@''HAVE_UNLINKAT''@|$(HAVE_UNLINKAT)|g' \
 	      -e 's|@''HAVE_USLEEP''@|$(HAVE_USLEEP)|g' \
 	      -e 's|@''HAVE_DECL_ENVIRON''@|$(HAVE_DECL_ENVIRON)|g' \
+	      -e 's|@''HAVE_DECL_FCHDIR''@|$(HAVE_DECL_FCHDIR)|g' \
 	      -e 's|@''HAVE_DECL_GETDOMAINNAME''@|$(HAVE_DECL_GETDOMAINNAME)|g' \
 	      -e 's|@''HAVE_DECL_GETLOGIN_R''@|$(HAVE_DECL_GETLOGIN_R)|g' \
 	      -e 's|@''HAVE_DECL_GETPAGESIZE''@|$(HAVE_DECL_GETPAGESIZE)|g' \